With the increasing down-scaling of integrated circuits and increasingly demanding requirements to the speed of integrated circuits, transistors need to have increasingly higher drive currents and smaller dimensions. To meet these conflicting requirements, Fin Field-Effect Transistors (FinFETs) were developed. FinFETs have greater channel widths than planar transistors. The increase in the channel widths is achieved by forming channels that include portions on the sidewalls of semiconductor fins and portions on the top surfaces of the semiconductor fins. Since the drive currents of transistors are proportional to the channel widths, the drive currents of the FinFETs are increased over that of planar transistors.
FinFETs are also made smaller and smaller, and the fins of the FinFETs are made thinner and thinner. To form such small fins, special optical technique such as diffraction and interference were used. This causes the formation process of the fins to be more complex.